Elevator Chain Selection Example

A centrifngal discharge bncket elevator has been selected to handle 3/4-in. lump coal to a belt system feeding snrge bins. Bnckets and some components are already on hand and should be used, if possible. Requirements are as follows  

To achieve a capacity of 60 tons/hr, the elevator has to carry an average of 8.33 Ib/ft, so the maximum permissible bucket spacing is 17 x 12/8.33 = 24.49 in. Therefore, buckets every fourth link of a 6-in. pitch chain will produce the rated capacity. 

On a centrifugal discharge bucket elevator, the shaft revolutions per minute, coupled with the radius of the bucket center, must be such that the bucket will discharge the material. Against this is that chains have limits to the speeds at which they may be operated. 

From Table 11-3 and Table 11-4, maximmn allowable speeds of a 6-in. pitch chain in bucket elevator service is 37 rpm shaft speed and 203 ft/min hnear chain speed over an 11-tooth sprocket. Over a 12-tooth sprocket, these values are 41 rpm and 246 ft/min, and for a 13-tooth sprocket they 

the minimum shaft revolutions per minute necessary so that bucket discharge will be satisfactory must be determined. Calculating the pitch diameter of a 12-tooth sprocket for 6-in. pitch chain (securing the necessary angle cosecant from Table 4-7) 6 in. X 3.8637 = 23.18 in. 

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In 1983, a quarterpolymer of tetrafluoroethylene and ethylene was reported in which hexafluoropro-pylene and a vinyl monomer with bulky side chains were the third and fourth monomers. The incorporation of these two comonomers improved the tensile strength and break elongation of the quarterpolymers at elevated temperatures. These polymers are suitable for the fabrication of extruded articles, monofilaments, andwire-coatings. Polymer composition ranged from 30-55% tetrafluoroethylene, 40-60% ethylene, 1.5-10% hexafluoropropylene, and 0.05-2.5% of a vinyl monomer. The fourth monomer could be selected from a variety of vinyl compounds including examples shown below and other more complex compounds ... 

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